PROJECT SUMMARY This application is in response to the funding opportunity ?Alcoholic hepatitis clinical and translational network ? basic and preclinical research (RFA-AA-18-006) under UH2/UH3 funding mechanism?. The goals of our application are to stimulate innovative basic/pre-clinical research to facilitate our understanding on the role of miR-21 in AH. We propose an exploratory yet novel approach to generate animal model targeting cell-type specific miR-21 in the liver. As a proof of concept to support our approach, we have generated hepatocyte specific miR-21-/- mice. Using the loss of function approach, we found, for the first time the connection between miR-21 and lipid metabolism, that hepatocyte miR- 21-/- mice are more sensitive to hepatic steatosis after alcohol feeding. As part of UH2 phase (Yrs 1 and 2), we will further explore the phenotypes of hepatocyte miR-21-/- mice in response to alcohol feeding and also propose to assess the feasibility of creating two new experimental animal models by generating KC-specific and HSC-specific miR-21-/- mice, respectively. As one of the goals of this funding mechanism, our proposal during the UH2 phase will lead to a breakthrough in the development of animal models specifically targeting miR-21 that could have a major impact on AH field. The success of the study during the UH2 phase will lead us to the UH3 validation phase to further explore the in-depth mechanistic study on the role of miR-21 in AH (Yrs 3-5) and to translate the understanding of the basic molecular mechanism by integrating our data into the AH network patient-oriented research setting to further determine the prognostic significance of miR-21 in patients with AH (Yrs 4-5).